The present invention is particularly applicable to installing and locking reels carrying magnetic tapes on magnetic tape winders. In existing data processing systems, magnetic tape winders are widely employed because magnetic tapes have great storage capacity. In currently available magnetic tape winders, a single removable magnetic tape is replaced by another magnetic tape as soon as write and/or read operations relating to the tape have been completed. The tape winder includes first and second reels which carry the tape. The reels alternately receive and supply the magnetic tape to write and/or read heads. Each reel is driven by an electric motor via a direct mechanical linkage. The tape is intermittently driven in either direction relative to the read-write heads such that a relatively small or zero gap exists between the heads and tape. The tape travels at constant, relatively high speeds in a series of accelerations and decelerations having very short durations. Read operations occur in either direction of travel, while write operations occur only as the tape is traveling in one direction.
As a tape winder is being used, it is necessary frequently to change the tape and feed reel associated therewith on a particular winder. Because feed reel changing operations should be performed as rapidly as possible, the changes should be uncomplicated and involve a minimum number of actions on the part of an operator. It is also necessary during tape winding conditions, in either direction, for the reel to be effectively locked on a shaft of the winder motor. Otherwise, reliable operation of the tape winder is not assured. Thus, devices for securing magnetic tape reels on winder motor shafts should be simple in conception, easy to apply to and remove from the reel, and assure reliable and effective reel locking to the shafts. Reel securing devices, i.e., reel carriers, fulfilling these requirements are known. However, each of them has certain shortcomings.
One prior art reel securing device includes a circular rubber ring that selectively contacts a circular surface of a central hole of a reel. The ring is carried by a movable, circular element, situated on a hub of the reel carrier, which hub is integral with the motor shaft. The movable circular element is typically actuated by an electromagnet. After the reel has been placed on the reel carrier, the electromagnet is actuated such that the diameter of the movable element increases, whereby the movable element compresses the rubber ring between the reel carrier and the reel to lock the reel to the reel carrier, causing the reel to be immobilized in rotation with respect to the reel carrier. A disadvantage of this device is that the rubber ring has been found to deteriorate rapidly. Furthermore, the rubber ring tends to stick occasionally against the surface of the central hole in the reel. Also, it is difficult to automate this prior art device.
A second type of device for fastening a reel on a motor shaft includes a plurality of movable pads carried by shoes integral with the reel carrier hub. The pads selectively contact the surface of the reel central hole. The shoes are operated by a plurality of small rods, integral with a bar passing through the motor shaft. The small rods are driven by an electromagnet positioned at one extremity of the motor shaft. When it is intended to lock the reel on the reel carrier, the electromagnet is operated to thrust the bar so that it engages the shoes, causing the shoes to spread apart and drive the pads into contact with the surface of the central reel hole.
This prior art device requires a comparatively bulky and powerful electromagnet. While the electromagnet may be replaced by a pneumatic device operating a jack in response to high or low pressure, there are other disadvantages of this second device, relating to cost and complexity.
Both of the previously mentioned prior art devices require an internal means for supplying power to a fastening device that locks the reel on the reel carrier, i.e., an electromagnet or a pneumatic system. The internal devices for supplying power to the fastening device are comparatively heavy, bulky and operate only during extremely short time intervals, i.e., during operations when a reel is installed or removed. The internal devices for supplying power to the fastening devices are superfluous during data read and write operations associated with the magnetic tapes driven by the tape winder.
It is, accordingly, an object of the present invention to provide a new and improved method of and device for enabling an object to be easily secured to and removed from a motor shaft and which enables the object to be locked securely onto the shaft.
Another object of the present invention is to provide a new and improved method of and device for enabling magnetic tape reels to be easily secured to and removed from magnetic tape winders and for enabling the tape reels to be locked securely in situ on a motor shaft of the winder.
A further object of the invention is to provide a new and improved device for enabling magnetic tape reels to be secured to and removed from shafts of magnetic tape winders, wherein the devices do not require internal means for supplying power to a locking device for the reel on a reel carrier.
Still another object of the invention is to provide a new and improved method of and device for enabling magnetic tape reels to be secured to and removed from magnetic tape winder motor shafts, wherein the motor shaft supplies power to a fastening device for locking the reel on a reel carrier.
Still another object of the invention is to provide a new and improved, relatively easy to utilize, inexpensive, relatively simple, and small device for enabling an object to be secured to and removed from a shaft which is driven at a constant, relatively high speed and undergoes high acceleration and deceleration in either direction as it is driven to the constant speed, while maintaining the object in a locked condition on the shaft.